Selective call receivers known in the art are typically battery powered to allow for portability and convenience. As batteries have a limited energy content, reducing the current consumption of a selective call receiver helps to increase an operating duration of the selective call receiver.
One method of reducing the current consumption of the selective call receiver is to turn off its receiver circuitry when there are no radio signals intended for it. A substantial savings in current is obtained because the receiver circuitry consumes a large portion of the current supplied to the selective call receiver. Typically, the method skips over portions of a selective call signal and thereby saves current during specific time intervals of inactivity when the receiver circuitry is turned off. One prior art method which skips over the POCSAG synchronization codeword is adopted in U.S. Pat. Nos. 4,663,623 and 4,802,240 assigned.
However, the prior art methods to save current consumption by skipping over the synchronization codewords are unreliable because in skipping over the synchronization codewords, the selective call receiver may lose synchronization in decoding later portions of the selective call signal. A loss of synchronization results in errors when decoding the selective call signal or loss of the selective call signal completely. Furthermore, when the prior art method fails, the receiver will turn on for a longer period of time in an attempt to correct the failure and, thereby, cause an adverse increase in current consumption.
Thus, what is needed is a method to reduce current consumption in selective call receivers and yet maintain reliability in signal decoding.